1. Field of the Invention
The present invention relates to a nitrogen treating method for water to be treated (hereinafter, “water to be treated” will be referred to as “for-treatment water”) which contains organic nitrogen, nitrite nitrogen, nitrate nitrogen, nitrate ions, and ammonia.
2. Description of the Related Art
It has heretofore been well known that existence of nitrogen compounds is one of causes of eutrophication of rivers and lakes. Further, the nitrogen compounds exist in domestic waste water and industrial waste water in large amounts and are difficult to eliminate, and there are currently no effective countermeasures against removal of the nitrogen compounds. In general, a biological treatment is carried out. In the biological treatment, ammonia nitrogen contained in for-treatment water is converted into nitrate nitrogen or a nitrogen gas by denitrifying bacteria. Accordingly, the biological treatment has a problem that a treatment time is significantly long and a treatment efficiency is significantly low.
Further, there is another problem that since the denitrifying bacteria are significantly influenced by ambient temperature environment, components contained in the for-treatment water, and the like, particularly during the winter season when temperature is low, their activities are lowered, and a resultant reduction in denitrifying action causes efficiency of the treatment of the for-treatment water to be unstable.
Under such circumstances, to solve the foregoing technical problems, there is a method of converting ammonia nitrogen, nitrite nitrogen or nitrate nitrogen into a nitrogen gas through oxidation or reduction by passing an electric current through for-treatment water.
However, the conventional method of treating nitrogen compounds by electrolysis has a problem that while ammonia is produced from nitrate ions at a cathode, a reverse reaction in which nitrate ions are produced from the ammonia produced at the cathode occurs at an anode, resulting in a decrease in a treatment speed. Along with this, there exists an inconvenience caused by a reduction in efficiency of nitrogen removal.